In terms of a view (and the resulting photos) this location is awe-inspiring; more water carves its way through this narrow Fraser River canyon than goes over Niagara Falls each day.
The main attraction is the air tram spanning the river, and as you board you can hear the thundering water. The sound isn't all that surprising, considering 200 million gallons of water per minute crushes between the sides of the gorge. On the day I visited, the river's water level was 120 feet deep, and this was at the end of July when high water is already down considerably.
At the other end of the air tram is a quaint and very informative interpretive centre. There are things to see and do for all ages, which kept my family occupied nicely while I devolved into my natural shutterbug state.
I made a point to wander out over the river on the suspension bridge and made full use of the late morning lighting to photograph the river and the fish ladders (see right). These fish ladders are designed to help salmon make their journey up the Fraser to their spawning grounds; they're designed to slow the water down so the fish can have an easier time getting through the gorge, where the water gets a little rough and rowdy as it pushes through.
After lunch, I took some time with the family to check out the fudge factory. Yes, you heard me: a fudge factory. They had 23 different kinds when we were there, and I cleaned them out of the last of their espresso crunch fudge (which I can't stop eating, and now my wife has instituted a lunch-before-fudge rule).
Anyway there are many other things to check out and see, and a ton of great photo opportunities. Sometimes you don't have to go very far to find a completely new location and snap some dramatic pics, and I recommend you check out your own nearby tourist locations. Even if you roll your eyes at the thought of playing tourist, you shouldn't discount the opportunities waiting for you in your own neighbourhood. Tourist attractions draw tourists for a reason, and you can up your game by playing tourist with an SLR instead of a point-and-shoot or camera phone.
If you find yourself heading to Hell's Gate, I recommend bringing a wide-angle lens to grab more of that great landscape, a telephoto lens to zoom in on details that other tourists are likely to miss, definitely a tripod to help steady your shots and maybe set up some timed family portraits (including you), and last but not least, a big appetite for fudge.